Polarization Boosts Display Efficiency

ROCHESTER, N.Y. -- Displays are notoriously inefficient energy users, but scientists at the University of Rochester have developed an optical polarization method to change that, creating nearly perfect circularly polarized light.

"Polarized light is essential to optical information processing, display and storage," said Shaw H. Chen, professor of chemical engineering and materials science, and senior scientist at the university's Laboratory for Laser Energetics. "Traditionally, it is generated using polarizer sheets based on selective light absorption. The problem with this method is that up to 60 percent of the light is thrown away."

Researchers at the University of Rochester have created glassy liquid-crystal films that exhibit near-perfect circular polarization. The materials are shown fluorescing under UV excitation.
Instead, the team has produced a material that generates polarized light on the basis of selective reflection -- any light that does not have the right polarization state gets recycled for correction. Unlike today's displays, whose linear polarization must employ additional optical filters to produce color, this new material produces color polarized light, Chen noted.

Reporting their findings in the Feb. 11 issue of Nature, the researchers generated the almost pure circularly polarized light from films of glass-forming chiral-nematic liquid crystals that were doped with light-emitting substances.

"From an energy point of view, our material is much more efficient -- by a factor of two -- over the current technology," Chen said. "Because the polarization is circular, it also opens the door for more than just brighter, more efficient displays; it also means that 3-D displays can be realized."

Besides display applications, the material may be used to produce notch filters or to make latching electro-optic devices for optical communications, he said.

Kaiser Electronics in San Jose, Calif., has an exclusive license for the patented material technology for display and eyewear applications, although the company has not announced any commercialization time lines. The Rochester team is also working with several other companies on commercial and military initiatives, including Cornerstone Research Group in Dayton, Ohio, for Air Force applications.